1. Field of the Invention
The present invention relates to methods for manufacturing optical fibers and, more specifically, to methods for measuring the tension applied to optical fibers during manufacture.
2. Background of the Invention
The measurement of the draw tension applied to an optical fiber during an optical fiber drawing process is critical to the fiber drawing process. Excess draw tension applied to the optical fiber may damage the optical fiber or otherwise adversely effect the properties of the optical fiber. Moreover, excess draw tension may cause the optical fiber to break thereby resulting in costly process downtime while the optical fiber is rerouted through the system and the process is restarted. Current methods for measuring the draw tension applied to an optical fiber during the drawing process include optically measuring the birefringence of the optical fiber during the draw process. The birefringence of the optical fiber is strongly dependent on temperature and the optical properties of the optical fiber. Accordingly, draw tension measurements based on birefringence require regular calibration for each draw. Measuring the mechanical vibration of the optical fiber during the drawing process to determine the draw tension applied to the optical fiber is a more flexible alternative method for measuring the draw tension. However, mechanical vibrations in the optical fiber are susceptible to background acoustic noise generated or present during the drawing process. The acoustic noise may introduce error in the draw tension measurement.
Accordingly, a need exists for methods for measuring the tension applied to an optical fiber during a fiber drawing process which are easily calibrated and are not effected by acoustic noise in the fiber drawing process.